Add overwrite_arrays option

This is an extraction from
#103 where @dtaniwaki had
added this option, but had done it prior to the deep_merge extraction.

This depends on danielsdeleo/deep_merge#21

Paired with @carbonin <https://github.com/carbonin> on this.

README.md

@@ -258,6 +258,7 @@ You can customize `Config` only once, preferably during application initializati
 Config.setup do |config|
   config.const_name = 'Settings'
   config.knockout_prefix = nil
+  config.overwrite_arrays = false
 end
 ```
 
@@ -271,6 +272,8 @@ Inheritance customization (check [Deep Merge](https://github.com/danielsdeleo/de
 
 * `knockout_prefix` - ability to remove elements of the array set in earlier loaded settings file. Default: `nil`
 
+* `overwrite_arrays` - ability to replace an entire array set in earlier loaded settings file. Default: `false`
+
 ## Working with Heroku
 
 Heroku uses ENV object to store sensitive settings which are like the local files described above. You cannot upload

lib/config.rb

@@ -16,8 +16,9 @@ module Config
   @@use_env    = false
 
   # deep_merge options
-  mattr_accessor :knockout_prefix
+  mattr_accessor :knockout_prefix, :overwrite_arrays
   @@knockout_prefix = nil
+  @@overwrite_arrays = false
 
   def self.setup
     yield self if @@_ran_once == false

lib/config/options.rb

@@ -36,7 +36,10 @@ def reload_env!
         key.to_s.split('.').reverse.each do |element|
           hash = {element => hash}
         end
-        DeepMerge.deep_merge!(hash, conf, :preserve_unmergeables => false)
+        DeepMerge.deep_merge!(hash,
+                              conf,
+                              preserve_unmergeables: false,
+                              overwrite_arrays: Config.overwrite_arrays)
       end
 
       merge!(conf[Config.const_name] || {})
@@ -57,7 +60,8 @@ def reload!
           DeepMerge.deep_merge!(source_conf,
                                 conf,
                                 preserve_unmergeables: false,
-                                knockout_prefix: Config.knockout_prefix)
+                                knockout_prefix: Config.knockout_prefix,
+                                overwrite_arrays: Config.overwrite_arrays)
         end
       end
 
@@ -101,7 +105,10 @@ def to_json(*args)
 
     def merge!(hash)
       current = to_hash
-      DeepMerge.deep_merge!(hash.dup, current)
+      DeepMerge.deep_merge!(hash.dup,
+                            current,
+                            preserve_unmergeables: false,
+                            overwrite_arrays: Config.overwrite_arrays)
       marshal_load(__convert(current).marshal_dump)
       self
     end

spec/config_spec.rb

@@ -358,5 +358,37 @@
         end
       end
     end
+
+    context 'using overwrite_arrays' do
+      context 'in configuration phase' do
+        it 'should be able to assign a different overwrite_arrays value' do
+          Config.reset
+          Config.overwrite_arrays = true
+
+          expect(Config.overwrite_arrays).to eq(true)
+        end
+
+        it 'should have the default overwrite_arrays value equal false' do
+          Config.reset
+
+          expect(Config.overwrite_arrays).to eq(false)
+        end
+      end
+
+      context 'overwriting' do
+        let(:config) do
+          Config.overwrite_arrays = true
+          Config.load_files(["#{fixture_path}/overwrite_arrays/config1.yml",
+                             "#{fixture_path}/overwrite_arrays/config2.yml",
+                             "#{fixture_path}/overwrite_arrays/config3.yml"])
+        end
+
+        it 'should remove elements from settings' do
+          expect(config.array1).to eq(['item4', 'item5', 'item6'])
+          expect(config.array2.inner).to eq(['item4', 'item5', 'item6'])
+          expect(config.array3).to eq([])
+        end
+      end
+    end
   end
 end

spec/fixtures/overwrite_arrays/config1.yml

@@ -0,0 +1,17 @@
+array1:
+  - item1
+  - item2
+  - item3
+  - item4
+
+array2:
+  inner:
+    - item1
+    - item2
+    - item3
+    - item4
+
+array3:
+  - item1
+  - item2
+  - item3

spec/fixtures/overwrite_arrays/config2.yml

@@ -0,0 +1,12 @@
+array1:
+  - item2
+  - item4
+  - item5
+
+array2:
+  inner:
+    - item2
+    - item4
+    - item5
+
+array3: []

spec/fixtures/overwrite_arrays/config3.yml

@@ -0,0 +1,10 @@
+array1:
+  - item4
+  - item5
+  - item6
+
+array2:
+  inner:
+    - item4
+    - item5
+    - item6

spec/spec_helper.rb

@@ -43,9 +43,10 @@
 
       # Extend Config module with ability to reset configuration to the default values
       def self.reset
-        self.const_name      = 'Settings'
-        self.use_env         = false
-        self.knockout_prefix = nil
+        self.const_name       = 'Settings'
+        self.use_env          = false
+        self.knockout_prefix  = nil
+        self.overwrite_arrays = false
       end
     end
   end